Embodiments of the inventive subject matter generally relate to the field of wireless communication systems, and, more particularly, to techniques for mitigating adjacent channel interference.
The demand for wireless devices and services in the same unlicensed spectrum has increased the radio frequency interference for IEEE 802.11 devices. This interference can be caused by adjacent channel interference (ACI) caused by side band emissions from a signal in an adjacent channel. This interference limits the capacity and performance of a wireless communication system.
The problem of ACI is prevalent in the 2.4 GHz unlicensed spectrum where overlapping channels are used. The IEEE 802.11g standard allows for OFDM transmissions to operate within the same ISM frequency band, 2.4 GHz-2.435 GHz, as the IEEE 802.11b direct-sequence-spread-spectrum (“DSSS”) transmissions. The ISM frequency band is divided into 14 partially overlapping channels with each channel being 22 MHz wide and 5 MHz apart. Typically, filtering is used to minimize adjacent channel interference. However, there are times when filtering is not effective at reducing this interference and the side band energy falls within the pass band of a wireless receiver. With the increase in demand for IEEE 802.11g compliant wireless devices, adjacent channel interference will be a limiting factor for achieving reliable communications and performance.